Effect Of Nano-iron Substance On Anaerobic Biogas Production Performance Of Sludge

Excessive amounts of excess sludge that are randomly stacked or reclaimed without proper treatment and disposal will cause a series of environmental pollution problems,such as the occupation of land,the generation of malodorous gases,the breeding of mosquitoes and flies,the damage to the growth of animals and plants,and the pollution of water bodies.The use of appropriate sludge treatment and disposal technologies can not only eliminate the aforementioned series of environmental problems,but also recover resources and energy from them,which can turn waste into treasure,and achieve sustainable development.Anaerobic digestion is one of the most widely used processes for destroying and stabilizing sludge.This process stabilizes the sludge by converting part of the organic matter in the sludge into enewable energy-biogas,which can achieve the reduction,harmlessness and resource utilization of the sludge.However,the traditional anaerobic digestion process has the characteristics of long reaction period,low biogas production and low methane content.Therefore,finding new treatment technologies or additives to promote biogas production has become a research hotspot.In this paper,using certain solid-liquid ratio sludge as substrate,the effect of Nano-Fe₃O₄ and Nano-Fe⁰ on the anaerobic biogas production performance of the sludge was studied.Different concentrations of nano-iron materials were set up,and the optimum concentration was selected based on COD,ammonia nitrogen,and biogas production.Under the optimal conditions,the three-phase analysis of gas,liquid and solid in the anaerobic biogas production process was carried out to further explore the effect of Nano-Fe₃O₄ and Nano-Fe⁰on anaerobic biogas production performance of sludge.?1?The addition of Nano-Fe₃O₄ has a certain influence on the anaerobic biogas production process.The Nano-Fe₃O₄ concentration of 100 mg/L was maintained at600-1200 mg/L.The highest removal rates of TCOD and SCOD were 66.83%and73.05%,which were 8.35%and 9.90%higher than those of the blank group,respectively.In the blank group,the cumulative biogas production increased by28.08%,the biogas production cycle was shortened by 2 days,and the methane content increased by 6%.The change of ammonia was unstable when Nano-Fe₃O₄was added at 300 mg/L.The removal rates of TCOD and SCOD were the lowest,which were 60.83%and 62.20%,respectively.Compared with the blank group,they were increased by 2.35%and-0.95%respectively;the cumulative biogas production was lower than the blank.The experimental group with 300 mg/L Nano-Fe₃O₄ had a relatively stable pH value,indicating that the relatively high concentration of Nano-Fe₃O₄ had a good regulation effect on the pH of the system.In summary,the optimal concentration of Nano-Fe₃O₄ is 100 mg/L,and the worst concentration of Nano-Fe₃O₄ is 300 mg/L.?2?Experiments were conducted with the design mechanism of Nano-Fe₃O₄concentrations of 0,100,300 mg/L.From the gas phase,liquid phase and solid phase three-phase indicators,the system comprehensively discusses the influence mechanism of Nano-Fe₃O₄ addition on anaerobic gas production from sludge.For gas phase,the cumulative gas production in the promotion group is the largest,and the cumulative gas production in the suppression group is the smallest.For liquid-phase indicators,the promotion group maintains the ammonia nitrogen at the concentration suitable for the survival of microorganisms,and the yield of volatile fatty acids increases,and the pH value is maintained at between 7.2 and7.8,indicating that the appropriate amount of Nano-Fe₃O₄ is added to adjust the dynamic system of acid and alkali,ie to break The inhibitory steady state between volatile fatty acids and ammonia nitrogen releases Fe²⁺/Fe³⁺into the system,and its hydrolysis process can provide alkalinity for the anaerobic reaction system.Adding100 mg/L Nano-Fe₃O₄ can increase the degradation efficiency of TCOD by 3.6%,and increase the degradation rate of SCOD by 3.2%.This showed that adding proper amount of nano-tetra-iron tetroxide will accelerate the hydrolysis efficiency of sludge and thus promote organics in anaerobic digestion system.The degradation of the solid phase indicators,SEM showed that the blank group sludge structure is loose;promote the group sludge structure is tight,the gap is small.This shows that proper amount of Nano-Fe₃O₄ increases the contact area between microorganisms and sludge and adsorbs on the surface of microorganisms,thereby increasing microbial metabolic activity and accelerating methane production.The content of S element in the sludge treated with Nano-Fe₃O₄ at 100 mg/L is increased by element conservation.The law that the anaerobic process will produce a corresponding reduction of H₂S,indicating that the addition of Nano-Fe₃O₄ will reduce the anaerobic system to precipitate,reduce the production of hydrogen sulfide,and reduce the toxicity of methanogens.Infrared spectroscopy shows that anaerobic After the reaction,the organic content of sludge decreased.Thermogravimetric analysis showed that the ash content of sludge after anaerobic reaction increased,indicating that the addition of appropriate amount of Nano-Fe₃O₄ will accelerate the degradation of organic matter during the anaerobic reaction,thereby increasing the biogas production?3?The effects of different concentrations of NZVI on biogas production and methane content during anaerobic digestion were investigated.The reaction temperature was 35�C.The results showed that the 1000 mg/L NZVI histidine was maintained at 600-800 mg/L,the pH value was between 6.5⁸.0,and the CODCr degradation rate was increased by 2.91%.The NZVI group produced the highest content of VFAs,up to 3841.mg/L,and enhanced the use of acetic acid.Compared with the control group,cumulative biogas production increased by18.11%,which shortened the three-day biogas production cycle and increased the methane content by 6.93%.In summary,the optimal concentration of Nano-Fe⁰is 1000 mg/L.?4?The promotion mechanism of anaerobic digestion of sludge with 1000 mg/L NZVI.For the buffer system,the addition of NZVI increases the production and degradation of VFAs,has a great influence on the decomposition of propionic acid,increases the conversion of propionic acid,promotes the production of acetic acid,strengthens the utilization of acetic acid,and makes the ammonia nitrogen content change more obvious.In the range of 7.0 to 7.2,the fluctuation is small.The pH value is relatively stable,providing a suitable environment for the growth and metabolism of methanogens.For the organic degradation system,compared with the blank group,the TCOD degradation rate in the promotion group increased by23.13%,the SCOD degradation rate increased by 12.6%,and the VS removal rate was 8.86%.This shows that the addition of NZVI enhances the degradation of organicmaterialsandisconsistentwithinfraredspectroscopy.The thermogravimetry showed that the organic matter content of the sludge after anaerobic reaction was reduced,and the ash content was increased,further indicating that the addition of nano-iron improves the degradation of organic matter in the anaerobic process of the sludge and further increases the biogas production.For the microbiological system,the production of characteristic enzyme F₄₂₀20 in the promotion group increased by 35.8%compared with the blank group.The reduction in hydrogen sulfide production and the change in sludge morphology indicate that the addition of NZVI inhibits the activity of sulfate-reducing bacteria and promotes the activity of methanogenic bacteria,thereby increasing the anaerobic gas production efficiency of sludge.